Acoustic wave devices using an acoustic wave are used for filters and duplexers of wireless communication devices such as mobile phone terminals. The acoustic wave devices include surface acoustic wave devices using a SAW (Surface Acoustic Wave) and bulk acoustic wave devices using a bulk acoustic wave. The surface acoustic wave devices include a SAW device having a comb-shaped IDT (Interdigital Transducer) electrode formed on a piezoelectric substrate, a Love wave device having an IDT electrode covered with a dielectric film, and a boundary acoustic wave device having an IDT electrode sealed. The bulk acoustic wave devices include a piezoelectric thin film resonator device having electrodes sandwiching upper and lower surfaces of a piezoelectric film, and a Lamb wave device using a Lamb wave.
The acoustic wave device includes a sealing portion that seals a functional element of the acoustic wave device so that an air-space is formed above the functional element including an electrode exciting an acoustic wave (an IDT electrode formed on the piezoelectric substrate or a pair of electrodes formed on the upper and lower surfaces of the piezoelectric film). This structure enables to secure a region to excite the acoustic wave and maintain characteristics of the acoustic wave device.
As communication devices are downsized, electronic component modules on which the acoustic wave device is mounted are required to be further downsized. To downsize the electronic component module, there has been known a technique that disposes an acoustic wave device inside a multi-layered wiring board formed by stacking a wiring layer such as a metal and an insulating layer such as a resin (e.g. Japanese Patent Application Publication No. 2007-312107).
In the electronic component module having the acoustic wave device embedded in the multi-layered wiring board, when a shock is applied to an electronic component mounted on the surface, the shock may be transmitted to the sealing portion of the internal acoustic wave device located inside crushing the air-space, and the seal may be thereby broken.